No, Okay guys.
Some examples of Pro Apps are:
FCP X
Aperture
Premier
Photoshop
It really depends. It's a weird question to ask. It's like asking if dating two supermodels is enough or should I sleep with four. The cheapest and most effective upgrade in a computer is the RAM. By that I mean when you are able to upgrade it yourself, such as on the 27" model, and not pay Apple's outrageous prices. Having more RAM helps running those apps, but whether you need it really depends on how much you do with them and how intensive it is. Considering that you felt a base-level 21" iMac would be enough for your users, clearly you don't intend to do much and your time isn't very expensive.
Will those apps run with 8GB? Yes.
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I currently run Mountain Lion on 4GB and it does fine.
Sure, but we all have very different ideas of what "fine" is and we use our computers differently so what is fine to you, will not be fine to another user. I cannot stand when a computer pauses because I am running out of memory and the drive is being used to page out into virtual memory. Considering how cheap RAM is (if you don't buy it from Apple) then it seems insane to me to cheap out on it. Unless you use your computer to write mails and only run two applications at the same time. Your anecdotal evidence does not help in threads like these when the person needs has no idea what RAM is used for.
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I'm wondering this same thing. I want the new 21.5" iMac and was really disappointed to see you can't upgrade the RAM yourself. Anyone out there reading this who has the new iMac with 8GB and runs heavy programs like these:
Xcode
Photoshop
Final Cut
Excel
10 tabs open in Chrome!
Please let me know if 8GB can handle this load. I'm on a 2008 MacBook with 2GB and having two of those things open at once causes some serious slowdowns. If I get the new 21.5" iMac and have lets say Xcode, Photoshop, and a bunch of Chrome tabs open, will the computer still be fast? Or should I look into a hackintosh or some other alternative?
Again, it depends. What are you doing in Xcode, Photoshop and Final Cut? Are you writing a "Hello world" app or a real and complex application? Are you editing the photos from your iPhone in Photoshop or working on massive files? Are you planning to use all of them at the same time?
OS X in general loves RAM and caches aggressively. If you give it more RAM, then it will use that too, up to a point. Even Windows loves RAM. I am sitting in Bootcamp right now. Can you guess how much free RAM of my 16 GBs I have right now? 0 MB. Yep, it's using all available RAM to cache and it's running beautifully and smoothly. Not having enough RAM is off sided by having fast storage, since that's what has to be used when the memory manager runs out of RAM. But, even the fastest consumer SSDs are still 10 times slower than 1333 MHz RAM, and 1600 MHz RAM is slightly faster than that. The storage system, even if it's the fastest SSD available, is still basically the slowest component in your computer.